Oscillator and electronic device

ABSTRACT

Provided is an oscillator ( 100 ) including a piezoelectric body ( 70 ) that has a plurality of protrusions ( 72 ) on one surface thereof, a plurality of electrodes ( 80 ) that are respectively provided on the plurality of protrusions ( 72 ) so as to be separated from each other, and a plurality of electrodes ( 82 ) that are provided on the other surface opposite to the one surface of the piezoelectric body ( 70 ) so that each of the electrodes faces only one electrode ( 80 ). Thus, it is possible to prevent variation in acoustic characteristics from occurring. Therefore, the oscillator capable of improving the acoustic characteristics of an electronic device is provided.

TECHNICAL FIELD

The present invention relates to an oscillator having a piezoelectricvibrator, and an electronic device.

BACKGROUND ART

As an electro-acoustic transducer installed in an electronic device,there is a piezoelectric electro-acoustic transducer. The piezoelectricelectro-acoustic transducer generates a vibrational amplitude by usingan expansion and contraction motion that occurs by applying an electricfield to a piezoelectric vibrator. Since the piezoelectricelectro-acoustic transducer does not require a large number of membersin order to generate the vibrational amplitude, there is an advantage ina reduction in the thickness thereof.

A technique involved in the piezoelectric electro-acoustic transducer isdisclosed in, for example, Patent Document 1 and Patent Document 2. Inthe technique disclosed in Patent Document 1, a piezoelectric elementand a vibrating film are bonded to each other through a vibrationtransfer member having elasticity. In the technique disclosed in PatentDocument 2, piezoelectric bodies separated from each other are providedon a supporter.

A technique involved in a piezoelectric element is also disclosed in,for example, Patent Documents 3 to 8. Patent Documents 3 and 4 disclosea technique regarding an ultrasound wave probe using a piezoelectricelement. In a technique disclosed in Patent Document 5, a damper memberis buried in a groove that is formed in a piezoelectric ceramic element.Patent Document 6 discloses a technique relating to a piezoelectricactuator, in which a protruding portion is formed coming in contact withan elastic member and a moving element. In a technique disclosed inPatent Document 7, vibrating electrodes provided on two principalsurfaces of a piezoelectric element are pressed for electricalconduction therebetween without applying a conductive paste thereto. Inaddition, Patent Document 8 discloses a method of manufacturing apiezoelectric actuator.

RELATED DOCUMENT Patent Document

[Patent Document 1] Pamphlet of International Publication WO.2005/094121

[Patent Document 2] Japanese Unexamined Utility Model RegistrationPublication No. S62-10594

[Patent Document 3] Japanese Unexamined Patent Publication No. H5-41899

[Patent Document 4] Japanese Unexamined Patent Publication No. H9-84193

[Patent Document 5] Japanese Unexamined Utility Model RegistrationPublication No. S62-148000

[Patent Document 6] Japanese Unexamined Patent Publication No. H7-163166

[Patent Document 7] Japanese Unexamined Patent Publication No. H5-75372

[Patent Document 8] Japanese Unexamined Patent Publication No.2006-332616

DISCLOSURE OF THE INVENTION

For example, the piezoelectric electro-acoustic transducer is configuredby arranging a plurality of oscillators each having a piezoelectricvibrator in an array. In this case, variation in characteristics occursbetween a plurality of the piezoelectric vibrators. Thus, acousticcharacteristics of the electronic device deteriorate. Therefore, thereis a demand for a reduction in the variation in characteristics betweenthe piezoelectric vibrators in order to improve the acousticcharacteristics of the electronic device.

In addition, in order to improve the acoustic characteristics of theelectronic device, it is preferable to improve a sound pressure level ofan oscillator included in the electronic device.

An object of the invention is to improve the acoustic characteristics ofan electronic device.

According to a first invention, provided is an oscillator comprising: apiezoelectric body that has a plurality of first protrusions on onesurface thereof; a plurality of first electrode layers that arerespectively provided on the plurality of first protrusions so as to beseparated from each other; and a plurality of second electrode layersthat are provided on the other surface opposite to the one surface ofthe piezoelectric body so that each of the second electrode layers facesonly one first electrode layer.

According to a second invention, provided is an oscillator comprising: apiezoelectric vibrator; a vibration member that constrains thepiezoelectric vibrator on one surface thereof, and of which the end isbent toward one surface side or the other surface side opposite to theone surface; and a supporting member that holds the end of the vibrationmember.

In addition, according to the second invention, provided is anelectronic device comprising: a supporting member; and a plurality ofoscillators that are fixed onto the supporting member, wherein theoscillator includes: a piezoelectric vibrator; and a vibration memberthat constrains the piezoelectric vibrator on one surface thereof, andof which the end is bent toward one surface side or the other surfaceside opposite to the one surface and is held by the supporting member.

According to the invention, it is possible to improve acousticcharacteristics of an electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned objects, other objects, features and advantages willbe made clearer from the preferred embodiments described below, and thefollowing accompanying drawings.

FIG. 1 is a cross-sectional view illustrating an oscillator according toa first embodiment.

FIG. 2 is a plan view illustrating the oscillator shown in FIG. 1.

FIG. 3 is a plan view illustrating a modified example of the oscillatorshown in FIG. 1.

FIG. 4 is a cross-sectional view illustrating an electronic deviceaccording to a second embodiment.

FIG. 5 is a pl an view illustrating the electronic device shown in FIG.4.

FIG. 6 is a cross-sectional view illustrating a piezoelectric vibratorshown in FIG. 4.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the invention will be described withreference to the accompanying drawings. In all the drawings, likeelements are referenced by like reference numerals and descriptionsthereof will not be repeated.

FIG. 1 is a cross-sectional view illustrating an oscillator 100according to a first embodiment. The oscillator 100 according to theembodiment corresponds to the first invention in the specification. Theoscillator 100 according to the embodiment comprises a piezoelectricbody 70, a plurality of upper electrodes 80, and a plurality of lowerelectrodes 82. For example, the oscillator 100 is installed in anelectronic device such as a cellular phone.

The piezoelectric body 70 has a plurality of protrusions 72 on onesurface thereof. The plurality of upper electrodes 80 are provided onthe plurality of protrusions 72, respectively, so as to be separatedfrom each other. The plurality of lower electrodes 82 are provided onthe other surface opposite to the one surface of the piezoelectric body70 so that each of the lower electrodes faces only one upper electrode80. Hereinafter, the configuration of the oscillator 100 will bedescribed in detail.

FIG. 2 is a plan view illustrating the oscillator 100 shown in FIG. 1.FIG. 2 illustrates a top surface of the oscillator 100. As illustratedin FIG. 2, the protrusions 72 and the upper electrodes 80 that arerespectively provided on the protrusions 72 are arranged, for example,in an array.

As illustrated in FIG. 1, for example, the piezoelectric body 70 has aplurality of protrusions 74 on the other surface thereof. The pluralityof protrusions 74 are provided on the other surface of the piezoelectricbody 70 so that each of the protrusions 74 overlaps only one protrusion72 when seen in a plan view. In the embodiment, the plurality ofprotrusions 72 and the plurality of protrusions 74 can be provided so asto be plane-symmetrical to each other based on a central surface that islocated between the one surface and the other surface of thepiezoelectric body 70 (not shown).

The piezoelectric body 70 is constituted by a material having apiezoelectric effect, for example, lead zirconate titanate (PZT) orbarium titanate (BaTiO₃), as a material having a high electro-mechanicalconversion efficiency.

The protrusion 72 and the protrusion 74 are formed by processing thepiezoelectric body formed of the above-described material having apiezoelectric effect. The processing of the piezoelectric body can beperformed through, for example, cutting work of a piezoelectric materialor baking using a shape mold.

The protrusion 72 and the protrusion 74 have, for example, a squareshape when seen in a plan view.

The piezoelectric body 70 is polarized in the thickness directionthereof (vertical direction in FIG. 1). It is preferable that thepiezoelectric body 70 have a thickness of equal to or less than 1 mm ina portion where the protrusion 72 and the protrusion 74 overlap eachother when seen in a plan view. When the thickness exceeds 1 mm, theelectric field intensity of the piezoelectric body 70 decreases, whichresults in a decrease in energy conversion efficiency. In addition, itis preferable that the piezoelectric body 70 have a thickness of equalto or more than 10 μm in a portion where the protrusion 72 and theprotrusion 74 are not located. When the thickness is less than 10 μm,there is a concern that the piezoelectric body may be damaged duringhandling because the piezoelectric body 70 is constituted by a brittlematerial.

For example, the upper electrode 80 can be provided so as to have thesame shape as the protrusion 72 when seen in a plan view. In addition,for example, the lower electrode 82 can be provided so as to have thesame shape as the protrusion 74 when seen in a plan view.

The upper electrode 80 and the lower electrode 82 are constituted by amaterial having an electrical conduction property, for example, silveror a silver/palladium alloy. Since silver is a low-resistance versatilematerial, there is an advantage from the viewpoint of a manufacturingcost and a manufacturing process. In addition, a silver/palladium alloyis a low-resistance material having an excellent oxidation resistanceand has an excellent reliability. The thicknesses of the upper electrode80 and the lower electrode 82 are preferably 1 μm to 50 μm. When thethicknesses are less than 1 μm, it is difficult to uniformly mold theupper electrode 80 and the lower electrode 82. On the other hand, whenthe thicknesses exceed 50 μm, the upper electrode 80 or the lowerelectrode 82 serves as a constraint surface with respect to thepiezoelectric body 70, which results in a decrease in the energyconversion efficiency.

The upper electrode 80 and the lower electrode 82 that face each other,respectively, and the piezoelectric body 70 located between the upperelectrode 80 and the lower electrode 82 constitute one piezoelectricvibrator 10. In other words, one piezoelectric vibrator 10 isconstituted by the upper electrodes 80 and the lower electrodes 82facing each other, respectively, and the protrusions 72 and theprotrusions 74 that are located between the upper electrodes 80 and thelower electrodes 82.

Thus, the oscillator 100 has a plurality of the piezoelectric vibrators10.

FIG. 3 is a plan view illustrating a modified example of the oscillator100 shown in FIG. 1. In the embodiment, the protrusion 72, theprotrusion 74, the upper electrode 80, and the lower electrode 82 have asquare shape when seen in a plan view. On the other hand, as illustratedin FIG. 3, the protrusion 72, the protrusion 74, the upper electrode 80,and the lower electrode 82 can have any of various shapes. For example,as illustrated in FIGS. 3( a), 3(b), and 3(c), the protrusion 72, theprotrusion 74, the upper electrode 80, and the lower electrode 82 can beprovided so as to have an oblong shape. In addition, the number ofarrangements thereof is not limited. Further, as illustrated in FIG. 3(d), for example, the protrusion 72, the protrusion 74, the upperelectrode 80, and the lower electrode 82 may be provided so as to have acircular shape or an elliptical shape when seen in a plan view.

In this manner, the shapes of the protrusion 72, the protrusion 74, theupper electrode 80, and the lower electrode 82 are selected, therebyallowing resonance frequencies of the plurality of piezoelectricvibrators 10 constituted by these to be selected.

In the plurality of piezoelectric vibrators 10 constituted by theprotrusions 72, the protrusions 74, the upper electrodes 80, and thelower electrodes 82, it is possible to set any interval between thepiezoelectric vibrators 10 adjacent to each other. Thus, it is possibleto prevent a sound wave from interfering between the plurality ofpiezoelectric vibrators 10.

As illustrated in FIGS. 1 and 2, for example, the oscillator 100includes a supporting frame 30 that holds the piezoelectric body 70. Forexample, the supporting frame 30 holds an edge of the piezoelectric body70. In addition, for example, the supporting frame 30 holds the entirecircumference of the piezoelectric body 70.

As illustrated in FIG. 1, the oscillator 100 includes a control unit 90and a signal generating unit 92.

The signal generating unit 92 is connected to each of the upperelectrodes 80 and each of the lower electrodes 82. The signal generatingunit 92 generates an electrical signal to be input to each piezoelectricvibrator 10 that is constituted by each upper electrode 80 and eachlower electrode 82.

The control unit 90 is connected to the signal generating unit 92, andcontrols the generation of a signal by the signal generating unit 92.The control unit 90 controls the generation of the signal by the signalgenerating unit 92 based on information that is input from the outside,and thus the control unit 90 can independently control the output of theplurality of piezoelectric vibrators 10.

When the oscillator 100 is used as a parametric speaker, the controlunit 90 inputs a modulated signal of the parametric speaker through thesignal generating unit 92. In this case, each piezoelectric vibrator 10uses a sound wave of equal to or more than 20 kHz, for example, 100 kHz,as a carrier wave of the signal.

A fundamental resonance frequency of the piezoelectric vibrator dependson a length of a contour shape of a vibration plane. In other words, asa resonance frequency shifts to a high frequency, the area of thepiezoelectric vibrator is reduced. For this reason, the oscillationfrequency of each piezoelectric vibrator 10 is set to be in anultrasound wave band, thereby allowing the size of the oscillator 100 tobe reduced.

In addition, the oscillation frequency of each piezoelectric vibrator 10is set to be in an ultrasound wave band, and thus a high directivity canbe realized.

In addition, when the oscillator 100 is used as a general speaker, thecontrol unit 90 may directly input a sound signal to each piezoelectricvibrator 10 through the signal generating unit 92.

In addition, when the oscillator 100 is used as a sound wave sensor, asignal to be input to the control unit 90 is a command signal to theeffect that a sound wave is oscillated. When the oscillator 100 is usedas a sound wave sensor, the signal generating unit 92 causes eachpiezoelectric vibrator 10 to generate a sound wave having a resonancefrequency of each piezoelectric vibrator 10.

Next, effects of the embodiment will be described. The oscillator 100according to the embodiment comprises the plurality of upper electrodes80 that are respectively provided on the plurality of protrusions 72included in the piezoelectric body 70 so as to be separated from eachother, and the plurality of lower electrodes 82 that are provided on theother surface of the piezoelectric body 70 so that each of the lowerelectrodes faces only one upper electrode 80. At this time, theplurality of protrusions 72, the plurality of upper electrodes 80, andthe plurality of lower electrodes 82 constitute the plurality ofpiezoelectric vibrators 10.

As such, according to the embodiment, the plurality of piezoelectricvibrators 10 are constituted by the single-layered piezoelectric body70. For this reason, the plurality of piezoelectric vibrators 10 arearranged in an array, and thus a process of bonding them to each otheris not required. It is possible to prevent variation in characteristicsfrom occurring between the plurality of piezoelectric vibrators 10.Therefore, it is possible to improve the acoustic characteristics of theelectronic device.

In addition, each piezoelectric vibrator 10 is independently controlledthrough each upper electrode 80 and each lower electrode 82. Thus, it ispossible to control the plurality of piezoelectric vibrators 10 with ahigh degree of freedom.

Each of the plurality of piezoelectric vibrators 10 is constituted byeach protrusion 72. In other words, the plurality of piezoelectricvibrators 10 are arranged by interposing grooves therebetween. Thus, ascompared with a case where no groove is formed between the piezoelectricvibrators 10, the vibration of the piezoelectric vibrator 10 isprevented from being constrained. Therefore, the energy loss of theoscillator 100 is reduced, and thus power consumption can be reduced.

In addition, the plurality of protrusions 72 are arranged by interposinggrooves therebetween. Thus, it is possible to prevent the vibration frombeing transferred from one piezoelectric vibrator 10 to another adjacentpiezoelectric vibrator 10.

FIG. 4 is a cross-sectional view illustrating an electronic device 200according to a second embodiment. In addition, FIG. 5 is a plan viewillustrating the electronic device 200 shown in FIG. 4. The electronicdevice 200 according to the embodiment corresponds to the secondinvention in the specification. The electronic device 200 according tothe embodiment comprises a supporting member and a plurality of theoscillators 100. For example, the electronic device 200 is a portableterminal device such as a cellular phone.

The plurality of oscillators 100 are fixed onto the supporting member.The oscillator 100 has the piezoelectric vibrator 10 and a vibrationmember 20. The vibration member 20 constrains the piezoelectric vibrator10 on one surface thereof. In addition, the end of the vibration member20 is bent toward one surface side or the other surface side opposite tothe one surface. Further, the end of the vibration member 20 is held bythe supporting member. Hereinafter, the configuration of the electronicdevice 200 will be described in detail.

The vibration member 20 has, for example, a flat plate shape. Thevibration member 20 is constituted by a material, such as a metal or aresin, having a high elastic modulus with respect to ceramic which is abrittle material, and is constituted by a versatile material such asphosphor bronze or stainless steel. The thickness of the vibrationmember 20 is preferably 5 μm to 500 μm. In addition, the modulus oflongitudinal elasticity of the vibration member 20 is preferably 1 GPato 500 GPa. When the modulus of longitudinal elasticity of the vibrationmember 20 is excessively low or high, there is a concern that vibrationcharacteristics and reliability of the oscillator may be damaged.

As illustrated in FIG. 4, the vibration member 20 is held by, forexample, a substrate 32. As illustrated in FIG. 5, the substrate 32 hasa hollow ring shape. The ring shape is, for example, quadrangular.However, the invention is not limited thereto, and the ring shape may becircular or elliptical. A portion of the end of the vibration member 20is fixed onto the substrate 32, and thus the vibration member 20 is heldby the substrate 32.

In addition, the substrate 32 is fixed using, for example, thesupporting frame 30.

As illustrated in FIG. 4, the end of the vibration member 20 is benttoward the one surface side. Since the end of the vibration member 20 isbent, the vibration member 20 has a spring shape. Thus, duringvibration, a flat spring effect acts on the vibration member 20. Inaddition, it is possible to increase the length of a stroke during thevibration. Therefore, a sound pressure level of the oscillator 100 canbe improved.

As illustrated in FIG. 4, the vibration member 20 is bent toward one ofone surface side and the other surface side at one end thereof and atthe other end opposite to the one end. In the embodiment, as illustratedin FIG. 4, both the one end and the other end of the vibration member 20are bent toward the one surface side. In addition, the vibration member20 is fixed to the substrate 32 at the one end and the other endthereof.

The vibration member 20 is bent at a bend portion 22.

In addition, when seen in a plan view, the end of the vibration member20 is located further inside than the bend portion 22. For this reason,a mounting area for the bent end of the vibration member 20 is notrequired. Therefore, it is possible to reduce a distance between thearranged oscillators 100 and to reduce the size of the electronic device200.

As illustrated in FIG. 4, for example, the plurality of oscillators 100are arranged on both surfaces of the substrate 32. In the embodiment, aplurality of oscillators 102 are arranged on one surface of thesubstrate 32, and a plurality of oscillators 104 are arranged on theother surface thereof. In addition, the oscillators 102 and theoscillators 104 are disposed so as to be mutually displaced when seen ina plan view.

According to the electronic device 200 in the embodiment, theoscillators 102 and the oscillators 104 are disposed so as to bemutually displaced when seen in a plan view. In addition, the substrate32 has a hollow ring shape.

For this reason, a sound wave that is output toward one surface side ofthe substrate 32 from the plurality of oscillators 102 and a sound wavethat is output toward one surface side of the substrate 32 from theplurality of oscillators 104 via gaps between the oscillators 102 areemitted toward one surface side of the substrate 32. In addition, asound wave that is output toward the other surface side of the substrate32 from the plurality of oscillators 104 and a sound wave that is outputtoward the other surface side of the substrate 32 from the plurality ofoscillators 102 via gaps between the oscillators 104 are emitted towardthe other surface side of the substrate 32.

Therefore, the sound waves that are output from the oscillators 102 andthe oscillators 104 are effectively emitted, and thus a high soundpressure level can be realized.

Meanwhile, the arrangement of the oscillators 102 and the oscillators104 can be arbitrarily adjusted.

FIG. 6 is a cross-sectional view illustrating the piezoelectric vibrator10 shown in FIG. 4. As illustrated in FIG. 6, the piezoelectric vibrator10 has the piezoelectric body 70, the upper electrode 80, and the lowerelectrode 82. The piezoelectric body 70 is interposed between the upperelectrode 80 and the lower electrode 82. In addition, the piezoelectricbody 70 is polarized in the thickness direction thereof (verticaldirection in FIG. 6). The piezoelectric vibrator 10 is, for example,circular or elliptical in shape in a plane direction horizontal to onesurface of the vibration member 20.

For example, the same as that of the first embodiment can be used as thepiezoelectric body 70. In addition, for example, the same as that of thefirst embodiment can be used as the upper electrode 80 and the lowerelectrode 82.

The electronic device 200 includes the control unit 90 and the signalgenerating unit 92.

The signal generating unit 92 is connected to each piezoelectricvibrator 10, and generates an electrical signal to be input to eachpiezoelectric vibrator 10. In addition, the control unit 90 is connectedto the signal generating unit 92 and controls the generation of a signalby the signal generating unit 92. The control unit 90 controls thegeneration of the signal by the signal generating unit 92 based oninformation that is input from the outside, and thus the control unitcan independently control the output of the plurality of oscillators100.

The output control of the oscillator 100 can be implemented using thecontrol unit 90 and the signal generating unit 92 in a similar manner tothe first embodiment.

Next, effects of the embodiment will be described. The electronic device200 according to the embodiment comprises a vibration member thatconstrains the piezoelectric vibrator 10 on one surface thereof, and ofwhich the end is bent toward one surface side or the other surface sideand is held by a supporting member.

According to the embodiment, the vibration member 20 has a spring shape.For this reason, during vibration, a plate spring effect acts on thevibration member 20. In addition, it is possible to increase the lengthof a stroke during the vibration. Thus, a sound pressure level of theoscillator 100 can be improved. Therefore, the acoustic characteristicsof the electronic device can be improved.

As described above, although the embodiments of the invention have beenset forth with reference to the drawings, they are merely illustrativeof the invention, and various configurations other than stated above canbe adopted.

The application claims priority from Japanese Patent Application No.2011-081025 filed on Mar. 31, 2011, the content of which is incorporatedherein by reference in its entirety.

1. An oscillator comprising: a piezoelectric body that has a pluralityof first protrusions on one surface thereof; a plurality of firstelectrodes that are respectively provided on the plurality of firstprotrusions so as to be separated from each other; and a plurality ofsecond electrodes that are provided on the other surface opposite to theone surface of the piezoelectric body so that each of the secondelectrodes faces only one first electrode.
 2. The oscillator accordingto claim 1, further comprising a plurality of second protrusions thatare provided on the other surface of the piezoelectric body so that eachof the second protrusions overlaps only one first protrusion when seenin a plan view.
 3. The oscillator according to claim 1, furthercomprising: a signal generating unit that is connected to each of thefirst electrodes and each of the second electrodes; and a control unitthat controls generation of a signal by the signal generating unit,wherein the first electrode and the second electrode that face eachother, and the piezoelectric body that is interposed between the firstelectrode and the second electrode constitute one piezoelectricvibrator, and wherein the control unit controls the generation of thesignal by the signal generating unit to independently control the outputof a plurality of the piezoelectric vibrators.
 4. An oscillatorcomprising: a piezoelectric vibrator; a vibration member that constrainsthe piezoelectric vibrator on one surface thereof, and of which the endis bent toward one surface side or the other surface side opposite tothe one surface; and a supporting member that holds the end of thevibration member.
 5. The oscillator according to claim 4, wherein thevibration member is bent toward one of the one surface side and theother surface side at one end thereof and the other end opposite to theone end.
 6. The oscillator according to claim 4, wherein the vibrationmember is bent at a bend portion, and the end thereof is located furtherinside than the bend portion when seen in a plan view.
 7. An electronicdevice comprising: a supporting member; and a plurality of oscillatorsthat are fixed onto the supporting member, wherein the oscillatorincludes: a piezoelectric vibrator; and a vibration member thatconstrains the piezoelectric vibrator on one surface thereof, and ofwhich the end is bent toward one surface side or the other surface sideopposite to the one surface and is held by the supporting member.
 8. Theelectronic device according to claim 7, wherein the vibration member isbent at a bend portion, and the end thereof is located further insidethan the bend portion when seen in a plan view.
 9. The electronic deviceaccording to claim 7, wherein the plurality of oscillators are arrangedon both surfaces of the supporting member.